Process for the extraction of metals



Patented Sept. 22, 1925.

UNITED STATES, VPFATENT OFFICE.

EDWIN w. HALE-F GREEHWICH, CONNECTICUT, AN!) CoLIN e. rINx, or YoNxEn s,,NEW YORK, ASSIGNORS or o E-nALr-To THE nonn OMPANY, A CORPORATION 012"DELAWARE.

1T0 Drawing. Application filed June 8,

Ta-all whom it may concern:

Be it known that we, EDWIN W. HALE and COLIN G. FINK, citizens of theUnited States, residing at Greenwich, in the county 6 of Fairfield andState of Connecticut, and Yonkers, in the county of Westchester andState of New York, respectively, have "invented-certain new and usefulImprovements in Processesfor the Extraction of Metals, of

10 which the following is a specification.

Our process relates to the extraction of metals informs soluble in asolution of bromine.

, In the practice of our process bromine is dissolved in a salt solutionpreferably of a halogen salt in which it is readily soluble andWith'thisliquid the finely ground ore,

compound or concentrates containing metal.

'in a form soluble in. a solution of bromine are leached, whereby isobtained elemental sulphur" (if the metal was originally presentassulphide) and a solution of the bromide of the metal. The sulphur andgangue are removed and the solution is subjected to the "action of acurrent in an electrolytic cell, whereby the metal is deposited andbromine is liberated and held, in solution in the liquid. Theelectrolytic treatment should not proceed to the point of complete 13deposition of the metal contents, because if that. were done the brominewould be thrown out of solution, since it isless soluhis in liquid freefrom halogen salts. Hence, the li uid should be removed from the cellwhile it contains enough halogen salt to re tain in solution the bromineliberated therein. This liquid may then be used to leach a fresh batchof ore or concentrates and the rocess made a continuous one with smalloss of reagents.

The following is an example of one way of practicing our invention butour claims are not limited thereto orthereby:

convenient method of obtaining the J leaching liquidto wit, brominedissolved in asolution of a halogen salt-is the following: A solutioncontaining, say, twent ,i five grammes of zinc per litre asbromi e, oras a mixture of chloride and bromide, is W made up. This may be preparedby dissolving the salt or salts in water, or by treating zinc'dust withasolution of bromine dissolved in aezinc chloride solution. llf amixture of the two halogen salts is used, they 1922. Serial No. 566,848.

duced into an electrolytic cell which may bet equipped with carbonplates as electrodes and a current of, say, fifteen amperes persquarefoot of cathode surface passed between the electrodes. The result'is the libtom of the cell, not as liquid bromine, but as a solution ofbromine in the undecomposed cell liquor. Being at the bottom of theeration of bromine, which sinks to the botcell, this solution is notexposed to evaporation and loss ofbromine into the air. Electrolysis isnot carried to the complete extraction of the zinc, or near it, becauseif it were, the bromine would separate out as liquid bromineundissolved' in the electrolyte. If a mixture of chloride and bromide orof sulphate, chloride and bromide of zinc be present, the bromine is thefirst anion to be liberated, and as chlorine or sulphate is cheaper thanbromine, a mixture of the two zinc salts makes a serviceable medium, thezinc chloride or/and zinc sulphate merely acting as a carrier for theliberated bromine.

The liquid'fiowing from the cell, containing free bromine correspondingin equivalent amount to the zinc whichhas been deposited upon thecathode, is the liquid employed in the leaching process. In place ofzinc salts, other salts may be used as carriers of the bromine orbromide.

Having thus obtained a suitable leaching liquid, a continuous process ofpracticing our invention is the following: Finely ground zinc-sulphideore, or concentrate of zinc sulphide, is agitated with theabove-described liquid, whereby the zinc sulphide is decomposed andforms zinc bromide, and

elemental sulphur is left with the gangue a will subsequently recovered.llf lead is present in the ore, it is left behind for the host part 'theelectrolytic cell, apparently reaching a -chem1cally-pure zinc is notthe objectv sought.

i the electrolytic cell where, as above de- "as lead sulphate, but ifany is dissolved as point of equilibrium beyond which it does not buildup. A certain amount of iron in the product is permissiblein a processWhere Should there be an undue accumulation of impurities, means may beprovided for bleeding the system and thus keeping the impurities withindesired "bounds. The

zinc and bromine may be recovered from the portion bled from the systemin any suitable manner.

The purified liquid is then conducted to scribed, electrolysis is notcarried to the complete extraction of the zinc, or to the point whereany part of the bromine separates out as liquid bromine undissolved inthe electrolyte. The liquid discharged from the electrolytic cell isintroduced into agitators containing afresh batch of bre or concentrateand thesystem thus becomes a continuous one.

The cathode zinc deposited inthe cell is.

removed and, if preferred, melted, cast into plates and marketed withoutfurther. uri-- cation. The residue from the leac ing tanks contains freesulphur in a spongy condition which may be recovered as a. marketableroduct by suitable means, such as distillation and condensation; or theresidue may be solddirect to be used in any desired manner-for example,to be converted into su huric acid. r

. nstead of applying our process to the extraction-of zinc from zincsulphides, it may applied to the extraction of other metals in formssoluble in .a solution of. bromide, ,where the bromine is regenerated byelectrolysis for further leaching. What we claim-is:-

The step in the process of extracting me tals which are in combinationwith such other elements as t9 be capable of being decomposed by'bromine, which consists-in decomposing such metallic compounds bybromine in a solution of asalt in which it is more soluble than inwater. J

The process of extracting metals which are in combination with suchother elements as to be capable of being decomposed by bromine, whichconsists in decomposing such metallic compounds by bromine in a solutionof a salt in which it is more soluble than in water,partially depositingthe metal therefrom by electrolysis, discontinuing the electrical actionwhile the liberated bromineremains in solution and using the solution ofbromine resulting therefrom to treat additional compound of metal.

3. A step in the process of extracting zinc from zinc sulphide whichconsists in dissolving the zinc of the sul hide in bromine dissolved ina solution 0 a salt in which it is moresoluble than in water.

4. The process of extracting Zinc from zinc sulphide which consists indissolving the zinc of the sulphide in asolution of brominein a saltsolution in which it has greater solubility than in water and depositingthe zinc therefrom by electrolysis.

5. The process of extracting zinc from zinc sulphide ,.which consists inleaching with bromine or compounds ieldin bromine in solution forcombination wit zinc and subsequently depositing the metal andregenerating the bromineby electrolysis.

6. The process of extracting zinc from zinc sulphide which consists indissolving the zinc of the sulphidein bromine dissolved in a solution ofa salt in, which it is more soluble than in water, partially depositingthe zinc therefrom by'electrolysis, discontinuing the electrical action-while the 1iberated brominev remains in solution and using the solutionof bromine and bromide resulting therefrom to treat additional zinc sulhides. A

The processiof extract metals and sulphur from those metallic su phideswhich are decomposible with bromine, which consists in decomposing suchmetallic. sulphides by bromine dissolvedin a solution of a salt 100 I inwhich it. is more soluble than in water and depositing the metaltherefrom, and thereby regenerating the bromine, by electrolysis.

8. The process-of extracting zinc and sul- 105 phur, which consists indecomposing zinc sulphide by bromine dissolved in a solution of a saltand depositin the zinc therefrom,

and thereby regenerating the bromine, by 3 electrolysis.

' EDWIN W. HALE- v COLIN G. FIN K.

